US7063780B2 - Method for indirect-electrification-type continuous electrolytic etching of metal strip and apparatus for indirect-electrification-type continuous electrolytic etching - Google Patents

Method for indirect-electrification-type continuous electrolytic etching of metal strip and apparatus for indirect-electrification-type continuous electrolytic etching Download PDF

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US7063780B2
US7063780B2 US10/378,534 US37853403A US7063780B2 US 7063780 B2 US7063780 B2 US 7063780B2 US 37853403 A US37853403 A US 37853403A US 7063780 B2 US7063780 B2 US 7063780B2
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metal strip
series
etching
electrification
electrolytic etching
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US20030164307A1 (en
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Hisashi Mogi
Naruhiko Nomura
Shigenobu Koga
Masahiro Fujikura
Shuichi Yamazaki
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F7/00—Constructional parts, or assemblies thereof, of cells for electrolytic removal of material from objects; Servicing or operating
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/02—Etching
    • C25F3/06—Etching of iron or steel
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/02—Etching
    • C25F3/14—Etching locally

Definitions

  • the present invention relates to a method for indirect-electrification-type continuous electrolytic etching of a metal strip and an apparatus for the indirect-electrification-type continuous electrolytic etching, and, in particular, to a method for indirect-electrification-type continuous electrolytic etching of a metal strip suitable for producing a low-core-loss, grain-oriented silicon steel sheet, not susceptible to the deterioration of core loss after stress-relief annealing, used for the magnet core of a power supply transformer and the like, and an apparatus for the indirect-electrification-type continuous electrolytic etching.
  • a grain-oriented electrical steel sheet presently used for a practical application is easily magnetized in the direction of its rolling, and it is used mainly for electric machinery such as transformers.
  • electric machinery such as transformers.
  • Japanese Unexamined Patent Publication No. S60-211012 discloses a method for controlling secondary recrystallization by forming grooves on a cold-rolled steel sheet using a roll having protrusions, Japanese Unexamined Patent Publication No.
  • S62-86182 discloses a method for forming linear grooves periodically by spraying a solution of nitric acid to a final-annealed steel sheet
  • Japanese Unexamined Patent Publication No. S63-42332 discloses a method for forming grooves by electrolytic etching prior to final annealing.
  • examples of conventional technologies for improving material characteristics of a metal strip by forming an electrically insulating etching mask (etching resist) in a selective manner (in etching patterns) on a metal strip such as a steel sheet and continuously forming grooves on it by electrolytic etching include the inventions of production methods of a low-core-loss, grain-oriented electrical steel sheet suitable for use as the magnetic core of a transformer or other electric machinery, the inventions being disclosed in the Japanese Unexamined Patent Publication No. S63-42332 mentioned above, Japanese Examined Patent Publication H8-6140 and so on.
  • the direct electrification and indirect electrification methods have been studied in relation to continuous electrolytic etching.
  • an electrolytic etching apparatus for a metal strip with an electrically insulating etching resist applied to one of the surfaces, and has an electrolytic etching tank 2 , conductor rolls 16 functioning as anodes, back-up rolls 17 arranged in contact with the conductor rolls 16 with a metal strip 1 in between, a cathode 15 immersed in an electrolyte 3 in the electrolytic etching tank 2 , and immersion rolls 13 for immersing the metal strip 1 in the electrolyte 3 .
  • the metal strip 1 goes through the tank with its surface covered with the etching resist facing downward, and the cathode 15 is arranged so as to face toward the surface of the metal strip 1 covered with the etching resist and in a manner to keep a prescribed distance from the surface of the metal strip 1 covered with the etching resist.
  • the conductor rolls 16 are arranged so as to touch the surface of the metal strip 1 not covered with the etching resist and the back-up rolls 17 so as to touch the surface of the metal strip 1 covered with the etching resist, respectively.
  • the anodes and cathode are connected to a direct current power supply unit 7 and electrolytic etching is performed by directly electrifying the metal strip 1 .
  • the conductor rolls 16 are provided outside the electrolyte 3 in the electrolytic etching tank 2 , and, thus, a short circuit current is prevented from occurring.
  • the surface of a metal strip that can be electrolytically etched in one process using an electrically insulating etching resist formed into etching patterns is inevitably limited to the side of the metal strip not contacting the conductor roll, and, for this reason, when it is necessary to apply the electrolytic etching to both the surfaces of a metal strip, it is necessary to subject the metal strip to a total of two steps of the treatment process, one for each side, which fact leads not only to the problem of an elevated production cost but also to another of poor productivity.
  • the problems mentioned above are possibly solved by changing the method of the electrolytic etching from the direct electrification method to the indirect electrification method, but, as the electrolytic etching by the indirect electrification method is a technology not industrially applied in the past, there are various unclear issues in relation to the conditions of electrolytic etching, the stability of the product quality after the electrolytic etching (the shape of the grooves, and the like) and so forth, and, thus, it cannot be viewed as technically mature.
  • the present invention employs the continuous electrolytic etching technology by the indirect electrification, which has hitherto not been applied to industrial practice, and favorably solves the conventional problems of the indirect-electrification-type continuous electrolytic etching technology.
  • the present invention stabilizes the shape of the grooves to be formed through the etching and makes the width and depth of the grooves more even, realizes both the selectivity of processing subjects to enable the formation of grooves only on selected coils or steel sheets having good recrystallization and the controllability of the groove depth, and improves also the efficiency of the treatment of electrolyte.
  • the object of the present invention is to provide a method for indirect-electrification-type continuous electrolytic etching of a metal strip suitable, in particular, for producing a low-core-loss, grain-oriented silicon steel sheet, not susceptible to the deterioration of core loss after stress-relief annealing, used for the magnet core of a power supply transformer and the like, and an apparatus for the indirect-electrification-type continuous electrolytic etching.
  • the gist of the present invention which has been established for solving the above problems, is as follows:
  • a method for indirect-electrification-type continuous electrolytic etching of a metal strip characterized by, in applying voltage across the A series and B series electrodes, alternately repeating (I) a voltage application wherein an A series electrode becomes a cathode for a period of time M of 3 to 10 msec. and (II) a voltage application wherein the A series electrode becomes an anode for a period of time N of 4 ⁇ M to 20 ⁇ M msec.
  • a method for indirect-electrification-type continuous electrolytic etching of a metal strip according to the item (2) characterized by discontinuing the voltage application across the A series and B series electrodes for a period of time ⁇ msec. ( ⁇ >0) at the change from the voltage application of the item (I) to the voltage application of the item (II) and/or for a period of time ⁇ msec. ( ⁇ >0) at the change from the voltage application of the item (II) to the voltage application of the item (I).
  • a method for indirect-electrification-type continuous electrolytic etching of a metal strip according to any one of the items (1) to (3), characterized in that the final electrode within the electrodes arranged in the travelling direction of the metal strip is a B series electrode.
  • a method for indirect-electrification-type continuous electrolytic etching of a metal strip according to any one of the items (1) to (3), characterized by using, as the plural electrodes, a group of electrodes consisting of a pair of two electrodes, an A series electrode and a B series electrode lined up in said order in the travelling direction of the metal strip, as a minimum unit, per side of the metal strip.
  • a method for indirect-electrification-type continuous electrolytic etching of a metal strip according to any one of the items (1) to (3), characterized: in that the metal strip is a final-annealed grain-oriented silicon steel sheet having an insulating coating film on a surface; and by using the insulating coating film as the etching mask.
  • an insulating plate composed of an electrically nonconductive material, arranged between an A series electrode and a B series electrode adjacent to each other so as to face the same surface of the metal strip;
  • an electric power supply unit for performing the voltage control across an A series electrode and a B series electrode arbitrarily combining (I) a type of voltage control wherein an A series electrode becomes a cathode for a prescribed period of time M, (II) a type of voltage control wherein the A series electrode becomes an anode for a prescribed period of time N (N>M), and (III) a type of voltage control wherein a voltage is not applied to the A series electrode for a prescribed period of time.
  • An apparatus for indirect-electrification-type continuous electrolytic etching of a metal strip according to the item (13), characterized in that the final electrode within the electrodes arranged in the travelling direction of the metal strip is a B series electrode.
  • An apparatus for indirect-electrification-type continuous electrolytic etching of a metal strip characterized by arranging, as the plural electrodes, a group of electrodes consisting of a pair of two electrodes, an A series electrode and a B series electrode lined up in said order in the travelling direction of the metal strip, as a minimum unit, per side of the metal strip.
  • FIG. 1 is a schematic illustration, in the form of a longitudinal elevation view in section, of an apparatus for carrying out the method according to the present invention for continuously forming grooves by indirect-electrification-type electrolytic etching on a metal strip on which an etching mask is formed in etching patterns at least on one of the surfaces.
  • FIG. 2 is a diagram showing an example of the voltage application across electrodes a and b in the apparatus for carrying out the method according to the present invention in terms of the voltage of the electrode a.
  • FIG. 3 is a schematic illustration, in the form of a longitudinal elevation view in section, of an apparatus according to the present invention for continuously forming grooves by indirect-electrification-type electrolytic etching on a metal strip on which an etching mask is formed in etching patterns at least on one of the surfaces.
  • FIG. 4 is a diagram showing an example of the voltage application across an A series electrode and a B series electrode of the apparatus according to the present invention in terms of the voltage of the A series electrode.
  • FIG. 5 is a diagram showing another example of the voltage application across an A series electrode and a B series electrode of the apparatus according to the present invention in terms of the voltage of the A series electrode.
  • FIG. 6 is an illustration showing sectional shape patterns of the grooves formed by electrolytic etching in classification.
  • FIG. 7 is a schematic illustration, in the form of a longitudinal elevation view in section, of a conventional direct-electrification-type continuous electrolytic etching apparatus for a metal strip.
  • FIG. 8 is a schematic illustration, in the form of a longitudinal elevation view in section, of a conventional indirect-electrification-type continuous electrolytic pickling apparatus for a metal strip.
  • the present inventors continuously formed grooves by “electrolytic etching” on metal strips with an etching mask formed selectively (in etching patterns) on one surface and another etching mask covering all the other surface as in the “electrolytic pickling” described in said Japanese Unexamined Patent Publication No. H6-220699.
  • FIG. 1 schematically shows, in the form of a longitudinal elevation view in section, an apparatus for carrying out the method according to the present invention. Its main configuration is as follows. Facing the surface to be etched of a metal strip 1 continuously fed having an etching mask formed selectively (in etching patterns) on one of the surfaces, an electrode a 4 ′ and an electrode b 5 ′ are arranged in this order in the travelling direction of the metal strip. The space between the metal strip 1 and the electrodes a 4 ′ and b 5 ′ is filled with an electrolyte 3 .
  • a direct current electric power supply apparatus 7 is connected to the electrodes a 4 ′ and b 5 ′.
  • a switch 9 is provided between the direct current electric power supply apparatus 7 and the electrode a 4 ′, and, by closing the switch 9 , a voltage is applied across the electrodes a 4 ′ and b 5 ′ in a manner that the electrode a 4 ′ becomes an anode. By opening the switch 9 , the voltage application is discontinued.
  • conveyer rolls for the metal strip 1 wringer rolls 11 and 12 are provided at the entry and exit of an electrolysis tank 2 for preventing the electrolyte 3 from flowing out of the tank.
  • Sink rolls 13 and 14 are provided in the tank for maintaining the distance from the electrodes a 4 ′ and b 5 ′ to the metal strip 1 constant.
  • FIG. 2 An example of the voltage application across the electrodes a 4 ′ and b 5 ′ of the apparatus shown in FIG. 1 is shown in FIG. 2 in terms of the voltage of the electrode a 4 ′.
  • electrolytic current flows from the electrode a 4 ′ to the metal strip 1 through the electrolyte 3 and the etching pattern portion of the metal strip 1 facing said electrode, and then to the electrode b 5 ′ through the etching pattern portion of the metal strip 1 and the electrolyte 3 facing the electrode b 5 ′.
  • an insulating plate 6 made of an electrically nonconductive material is provided between the electrodes a 4 ′ and b 5 ′ in the electrolysis tank 2 .
  • the electrode a 4 ′ is an anode, in order that the electrode itself is not etched, an insoluble electrode of a Pt material is used for it.
  • the electrode b 5 ′ is a cathode and an electrode made of JIS SUS316 is used for it.
  • the present inventors applied voltage across the electrodes a and b in a manner shown in FIG. 2 in terms of the voltage of the electrode a, formed grooves by electrolytic etching on metal strips 1 having an etching mask formed selectively (in etching patterns), and observed the shape (geometrical shape, width and depth) of the grooves thus formed.
  • the metal strips 1 used here were final-annealed grain-oriented silicon steel sheets, and coating films of forsterite (Mg 2 SiO 4 ) forming during the final annealing and tension coating films (insulating coating films of a phosphate) on top of said coating films had been formed on both their surfaces through painting and then baking. On one of the surfaces, etching patterns had been formed in which the forsterite coating film and the tension coating film were selectively removed by a laser beam to expose the steel base material. Note that, as the tension coating film is an electrically insulating coating film, it can be used as an etching mask. An aqueous solution of NaCl was used as the electrolyte 3 .
  • forsterite Mg 2 SiO 4
  • tension coating films insulating coating films of a phosphate
  • the electrolytic etching is applicable by forming etching patterns beforehand on the surface(s) of the steel sheet.
  • Examples (i) to (iv) of observed shapes of the electrolytically etched grooves are shown in FIG. 6 .
  • the geometric shape of the grooves was very unstable and their width and depth were prone to fluctuate significantly. It was also observed that the percentage of the (i) U-shaped type groove shape, the most preferable, was comparatively low.
  • the present inventors formed grooves under different electrolysis conditions (NaCl concentration, electrolyte temperature, effective current density at the groove portions) on metal strips of different steel grades aiming at forming grooves having the (i) U-shaped type section shape, and investigated the shape of the grooves formed under the various conditions, but it proved difficult to stabilize the shape of the grooves and significantly reduce the fluctuation of their depth and width by these measures.
  • the present inventors devoted themselves to further studies and, focusing attention on the mass transfer within the grooves formed by the electrolytic etching and, in particular, on the stagnation of the electrolyte (precipitate from the solution), hit upon an idea that the shape of the grooves formed through the etching could be made stable and their width and depth more homogeneous by effectively reducing the stagnation and making the mass transfer smooth.
  • the present inventors conducted tests for verifying the idea and, as a result, they discovered that generating H 2 gas periodically for very short periods of time during the electrolytic etching process on the surface of the grooves formed was very effective as a measure for reducing the stagnation of the electrolyte (precipitate from the solution). This is explained below by referring to the attached drawings.
  • FIG. 3 schematically shows, in the form of a longitudinal elevation view in section, the construction of an apparatus according to the present invention for forming grooves by indirect-electrification-type electrolytic etching on a metal strip to be etched on one or both surfaces and having an etching mask formed in etching patterns at least on the surface to be etched.
  • the main configuration of the apparatus is as follows. Facing the surface to be etched of a metal strip 1 continuously fed having an etching mask formed selectively on one of the surfaces, an electrode A 4 and an electrode B 5 are arranged in this order in the travelling direction of the metal strip. The space between the metal strip 1 and the electrodes A 4 and B 5 is filled with an electrolyte 3 .
  • Direct current electric power supply apparatuses 7 and 8 are connected to the electrodes A 4 and B 5 .
  • Switches 9 and 10 are provided between the direct current electric power supply apparatuses 7 and 8 and the electrode A 4 , respectively, and, switches 9 ′ and 10 ′ are provided between the direct current electric power supply apparatuses 7 and 8 and the electrode B 5 , respectively.
  • an insulating plate 6 composed of an electrically nonconductive material is provided between the electrode A 4 and the electrode B 5 in the electrolysis tank 2 .
  • FIG. 4 shows an example of the voltage application across the electrodes A and B according to the present invention in terms of the voltage of the electrode A.
  • the electric circuit is so adjusted that a prescribed electrolysis current flows at the voltage application across the electrodes A and B to positively impress the electrode A 4 and the other to negatively impress the same.
  • a prescribed electrolysis current flows from the electrode A 4 to the metal strip 1 through the electrolyte 3 and the etching pattern portion of the metal strip 1 (functioning as a cathode) facing said electrode, and then to the electrode B 5 (functioning as a cathode) through the etching pattern portion of the metal strip 1 (functioning as an anode) and the electrolyte 3 facing the electrode B 5 .
  • the process of electrolytic etching proceeds at an etching pattern portion of the metal strip 1 on the side facing the electrode B 5 through the anodic reaction: Me ⁇ Me + +e ⁇ , (Fe ⁇ Fe 2+ +2 e ⁇ , when the metal strip is a steel strip).
  • either of the electrodes A 4 and B 5 becomes an anode or a cathode from time to time, and that, for this reason, it is desirable to make them of an insoluble material such as a Pt material in order that the electrode itself is not electrolytically etched when it is functioning as an anode.
  • the electrodes A and B are herein collectively referred to as the A series electrodes or B series electrodes, respectively, and, they may also be referred to simply as the electrodes A or electrodes B, respectively.
  • an A series electrode functions as a cathode and a B series electrode as an anode under the above voltage application (I)
  • M represent the period of time (msec.) of the voltage application
  • the voltage application is for a period of time M less than 3 msec.
  • the H 2 gas generation at the surface of the grooves formed by the etching is not sufficient for removing the stagnation of the electrolyte (precipitate) in the grooves
  • the voltage application is for a period of time M exceeding 10 msec., on the other hand, then the current efficiency of the electrolytic etching is lowered.
  • the period of time M is defined as 3 to 10 msec.
  • N represents the period of time (msec.) of the voltage application
  • the voltage application is for a period of time N less than 4 ⁇ M msec.
  • the current efficiency of the electrolytic etching is lowered
  • the voltage application is for a period of time N exceeding 20 ⁇ M msec.
  • the stagnation of the electrolyte (precipitate) in the grooves formed by the electrolytic etching becomes too large and it becomes difficult to remove the stagnation of the electrolyte (precipitate) from the grooves.
  • the period of time N is defined as 4 ⁇ M to 20 ⁇ M msec.
  • the arrangement of the electrodes wherein more than one pair of the electrodes A and B or more than one electrolysis tank are provided is explained below.
  • the final electrode in the travelling direction of the metal strip be a cathode.
  • each of the electrodes A and B is used as an anode and a cathode alternately from time to time according to the present invention
  • a B electrode functions as a cathode for most of the time.
  • the final electrode in the travelling direction of the metal strip be a B series electrode, which functions mainly as a cathode.
  • FIG. 5 shows an example of the voltage application across the A series and B series electrodes according to the present invention for solving such a problem, in terms of the voltage of the electrode A.
  • the present inventors applied voltage across the electrodes A and B of an apparatus shown in FIG. 3 in the manner shown in FIG. 5 in terms of the voltage of the electrode A, formed grooves by electrolytic etching on metal strips having an etching mask formed in etching patterns, and observed the shape (geometrical shape, width and depth) of the grooves thus formed. As a result, it was confirmed that the shape of the grooves formed through the electrolytic etching according to the present invention was made so stable that all of them had the U-shaped type section as shown in item (i) of FIG. 6 , and their width and depth became more even, exhibiting greatly reduced fluctuations.
  • the metal strips 1 used for the tests were final-annealed grain-oriented silicon steel sheets, and coating films of forsterite (Mg 2 SiO 4 ) formed during the final annealing, and tension coating films (insulating coating films of a phosphate system) on top of said coating films had been formed on both their surfaces through painting and then baking. On one of the surfaces, etching patterns had been formed in which the forsterite coating film and the tension coating film were selectively removed by a laser beam to expose the steel base material. Note that, as the tension coating film is an electrically insulating coating film, it can be used as an etching mask. A NaCl aqueous solution was used as the electrolyte 3 .
  • the electrolysis power supply apparatus to be employed in the present invention is not limited to the switching system using a direct current power supply apparatus and switches described before; any power supply method is acceptable as far as it is capable of realizing the voltage application cycles described earlier.
  • a system using a transistor or an inverter having a so-called 6-phase half-wave rectification waveform is also effective.
  • the present invention is effective for any case of continuously and stably forming grooves by indirect-electrification-type electrolytic etching on a metal strip to be etched at one or both surfaces and having an etching mask formed in etching patterns at least on the surface to be etched.
  • the other surface may be covered entirely with an etching mask or it may be left without any etching mask.
  • an apparatus for electrolytic etching of both surfaces of a metal strip can be configured simply by modifying the apparatus exemplified in FIG. 1 or 3 so that a group of electrodes and a power supply apparatus are provided for each of the upper and lower surfaces of the metal strip as in the apparatus shown in FIG. 8 . Therefore, in the present description, the apparatus for the electrolytic etching of both surfaces is not shown, with a drawing, as an example of the present invention.
  • the effect of the present invention is outstanding especially when the present invention is applied to a “stress-relief-annealing-resistant, low-core-loss, grain-oriented silicon steel sheet not susceptible to the deterioration of core loss by stress-relief annealing” produced through electrolytic etching of a final-annealed silicon steel sheet with an etching mask formed on the surfaces.
  • a stress-relief-annealing-resistant, low-core-loss, grain-oriented silicon steel sheet not susceptible to the deterioration of core loss by stress-relief annealing produced through electrolytic etching of a final-annealed silicon steel sheet with an etching mask formed on the surfaces.
  • the present invention is, naturally, effective also when applied to a grain-oriented silicon steel sheet having the tension coating films (insulating coating films of a phosphate system) formed by painting and an etching mask formed selectively on one of the surfaces but not having the forsterite (Mg 2 SiO 4 ) coating films.
  • the present inventors examined the dissolution of iron ions and the precipitation of iron hydroxide involved in the electrolytic etching. It became clear through the tests of the present inventors that, when the value of pH of the electrolyte was 7 or lower, iron dissolved in the electrolyte without forming precipitates and the disposal of the electrolyte was rendered easy. If iron precipitates, then piping is clogged, waste electrolyte disposal is hindered, and more maintenance work is required. For this reason, it is desirable to avoid the precipitation.
  • the value of pH of the electrolyte it is desirable to control the value of pH of the electrolyte to 2 or higher and 11 or lower.
  • the reason why the value of pH has to be 2 or higher is that, if it is below 2, the insulating coating film used as the etching resist material deteriorates. When the insulating coating film deteriorates, precise groove patterns will be destroyed, the electrolysis current will flow also to portions where grooves are not required, and these portions will be etched. Thus, the characteristic of the coating film as an etching resist becomes insufficient, and sharp grooves having a desired shape cannot be formed.
  • the reason why the value of pH has to be 11 or lower is that, if it exceeds 11, the insulating coating film deteriorates, the characteristic of the coating film as an etching resist becomes insufficient, and grooves of the intended U-shaped section cannot be formed.
  • the metal strips in these examples before electrolytic etching were grain-oriented silicon steel sheets cold-rolled to the final thickness, decarburization-annealed, painted with an anti-sticking agent for annealing consisting of MgO on both the surfaces and dried, then final-annealed, and having tension coating films (insulating coating films of a phosphate) formed through painting and baking on the coating films of forsterite (Mg 2 SiO 4 ) that had formed during the final annealing on both the surfaces.
  • They were also grain-oriented silicon steel sheets having, in addition, etching patterns formed on one of the surfaces by selectively removing the forsterite coating film and tension coating film using a laser beam to expose the steel base material. Note that, as the tension coating film was an electrically insulating coating film, it was used as the etching mask.
  • the grain-oriented silicon steel sheets pretreated as described above were subjected to an electrolytic etching treatment using an indirect-electrification-type continuous electrolytic etching apparatus as shown in FIG. 1 or 3 .
  • the shape patterns of the grooves formed through the electrolytic etching in the width direction of the steel sheets and the fluctuation of the groove depth were evaluated.
  • Table 1 shows the conditions of the test using an apparatus as shown in FIG. 1 or 3 and applying voltage as shown in any one of FIGS. 2 , 4 and 5 , and the results thereof.
  • Etching patterns each 0.3 mm in width, were formed at intervals of 6 mm by laser beam irradiation on steel sheets which had been finish-rolled to a thickness of 0.23 mm by cold rolling, final-annealed as grain-oriented electrical steel sheets and painted with insulating coating films, and, then, the steel sheets were processed in an electrolysis tank in which a cathode and an anode were arranged alternately so as to face the surface of the steel sheets where the steel base material was partially exposed.
  • a 5%-aqueous solution of sodium chloride was used as the electrolyte and its pH value was adjusted using sodium hydroxide and hydrochloric acid.
  • the etching was conducted under different values of pH ranging from 1 to 12.
  • Table 2 shows the result of the investigation of the amounts of iron precipitation in the electrolysis tank during the processing.
  • the amount of iron precipitation was measured, in terms of the weight of iron in the solution scooped up in a beaker, by retaining the iron in a filter paper.
  • the capacity of the electrolysis tank was 84 l
  • the effective current density at the groove portions was 600 A/dm 2
  • the values in the table are those after 40 sec. of processing in the electrolysis tank.
  • Etching patterns each 0.3 mm in width, were formed at intervals of 4 mm by laser beam irradiation on steel sheets finish-rolled to a thickness of 0.27 mm by cold rolling, final-annealed as grain-oriented electrical steel sheets and painted with insulating coating films. Then, the steel sheets having portions where the steel base material was exposed at one of the surfaces were processed in an electrolysis tank in which a cathode and an anode were arranged alternately so as to face said surface of the steel sheets.
  • a 3%-aqueous solution of potassium chloride was used as the electrolyte and its value of pH was adjusted using sodium hydroxide and hydrochloric acid. The etching was conducted under different values of pH ranging from 1 to 12.
  • Table 3 shows the result of the investigation of the amount of iron precipitation in the electrolysis tank during the processing.
  • the amount of iron precipitation was measured, in terms of the weight of iron in the solution scooped up in a beaker, by retaining the iron in a filter paper.
  • the capacity of the electrolysis tank was 84 l
  • the effective current density at the groove portions was 1,200 A/dm 2
  • the values in the table are those after 17 sec. of processing in the electrolysis tank.
  • Etching patterns each 0.3 mm in width, were formed at intervals of 6 mm on steel sheets finish-rolled to a thickness of 0.23 mm by cold rolling, final-annealed as grain-oriented electrical steel sheets and painted with insulating coating films. Then, the steel sheets having portions where the steel base material was exposed at one of the surfaces were processed in an electrolysis tank in which a cathode and an anode were arranged alternately so as to face said surface of the steel sheets.
  • a 7%-aqueous solution of calcium chloride was used as the electrolyte and its value of pH was adjusted using sodium hydroxide and hydrochloric acid. The etching was conducted under different values of pH ranging from 1 to 12.
  • Table 4 shows the result of the investigation of the amounts of iron precipitation in the electrolysis tank during the processing.
  • the amount of iron precipitation was measured, in terms of the weight of iron in the solution scooped up in a beaker, by retaining the iron in a filter paper.
  • the capacity of the electrolysis tank was 84 l
  • the effective current density at the groove portions was 700 A/dm 2
  • the values in the table are those after 40 sec. of processing on the processing line.
  • the precipitation began when the value of pH was raised to 6, and its amount increased significantly when the value of pH was 8 or higher. Therefore, by keeping the value of pH at 8 or higher within the above range of conditions, it was possible to dispose of the electrolyte after having iron precipitate effectively, and continuously form grooves on the final-annealed sheet materials.
  • the electrolyte was transferred from the electrolysis tank through a filter, with which the iron precipitate was collected, and then, after being stored once in a settling tank to have solids precipitate, to a waste liquor tank.
  • Etching patterns each 0.3 mm in width, were formed at intervals of 4 mm on steel sheets finish-rolled to a thickness of 0.27 mm by cold rolling, final-annealed as grain-oriented electrical steel sheets and painted with insulating coating films. Then, the steel sheets having portions where the steel base material was exposed at one of the surfaces were processed in an electrolysis tank in which a cathode and an anode were arranged alternately so as to face said surface of the steel sheets.
  • a 5%-aqueous solution of sodium nitrate was used as the electrolyte and its value of pH was adjusted using sodium hydroxide and hydrochloric acid. The etching was conducted under different values of pH ranging from 1 to 12.
  • Table 5 shows the result of the investigation of the amounts of iron precipitation in the electrolysis tank during the processing.
  • the amount of iron precipitation was measured, in terms of the weight of iron in the solution scooped up in a beaker, by retaining the iron in a filter paper.
  • the capacity of the electrolysis tank was 84 l
  • the effective current density at the groove portions was 1,200 A/dm 2
  • the values in the table are those after 20 sec. of processing on the processing line.
  • the precipitation began when the value of pH was raised to 5, and its amount increased significantly when the value of pH was 8 or higher. Therefore, by keeping the value of pH at 8 or higher within the above range of conditions, it was possible to have iron precipitate effectively, and to continuously form grooves on the final-annealed sheet materials.
  • the electrolyte was transferred from the electrolysis tank through a filter, with which the iron precipitate was collected, and then, after being stored once in a settling tank to have solids precipitate, to a waste liquor tank.
  • the present invention makes it possible to efficiently treat the electrolyte of the electrolytic etching.
  • the present invention provides a method for indirect-electrification-type continuous electrolytic etching of a metal strip suitable, in particular, for the production of a low-core-loss, grain-oriented silicon steel sheet not susceptible to the deterioration of core loss after stress-relief annealing used for the magnetic core of a power supply transformer and the like, and an apparatus for the indirect-electrification-type continuous electrolytic etching.

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WO2019148742A1 (zh) 2018-01-31 2019-08-08 宝山钢铁股份有限公司 一种耐消除应力退火的低铁损取向硅钢的制造方法

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WO2019148742A1 (zh) 2018-01-31 2019-08-08 宝山钢铁股份有限公司 一种耐消除应力退火的低铁损取向硅钢的制造方法

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